In this article we will read about what is osi model and 7 layers (what is osi model and its 7 layers) in very easy language and will read in detail about its benefits, disadvantages, what is layer. So let's start:
OSI Model - What is OSI Model
The full name of the OSI model is Open Systems Interconnection, developed by ISO (International Organization for Standardization) in 1978 and the model consists of 7 layers.
This is a reference model for communication between two users in a network.
Each layer of this model is independent but the transmission of data happened from one layer to another layer.
It describes how to send and receive data or information with in a network. Every layer of OSI model have their own different functions so that data can be easily accessed from one system to another.
OSI model also describes how network hardware and software function as layers with each other.
7 Layers of OSI MODEL - OSI model layer
OSI model has the following 7 layers, let's know them in detail: -
PHYSICAL LAYER
The physical layer is the lowest layer in the OSI model. The Physical layer is responsible for physical and electrical connections such as: - voltage, data rates etc.
In this layer the digital signal is converted into an electrical signal.
In this layer, the topology of the network i.e. the layout of network (network size) also functions in this layer.
This layer also describes whether the communication will be wireless or wired.
This is also called a bit unit.
Its functions
This layer defines how two or more devices connect physically together.
The physical layer defines transmission mode between two devices in the network.Simplex, half-duplex, and full duplex which will be used.
Data link layer
In OSI MODEL this is the second number layer from the bottom.This layer has two sub-layers: -
* MAC (Media Access Control), and
* LLC (Logic Link Control)
In data link layer, packets of data sent by the network layer are decoded and encoded.
This also ensures that these packets of data are error free.
This is also called a frame unit. This layer uses two protocols for data transmission.
1) high-level data link control (HDLC)
2) PPP (Point-to-Point Protocol)
3) Its functions
4) This layer translates physical raw bit stream into packets. We call these packets frames.Data Link layer adds header and trailer to these frames.
5) Its main function is to control flow.A fixed data rate is maintained from both ends receiver, sender. So that data is not corrupted.
6) It also controls the error.Cyclic Redundancy Check CRC is added with trailer in it so that there is no error in the data.
7) When two or more devices are connected to a communication channel, this layer determines which device is given access.
Network layer
The network layer is the third layer of the OSI model, this layer uses switching and routing technology. Logical address is function if this layer.
The data in the network layer is in the form of a packet (group of data) and the network layer is responsible for transporting these packets from the source to the destination.
The data link layer is also called a packet unit.
Its functions
Inter-networking is the main responsibility of the network layer. It provides logical connection between different devices.
Source and destination address is added to the header of the frame. The address is used to identify devices in the Internet.
The main work of this layer is routing which determines the best path (s).
Transport layer
Transport layer is fourth layer of OSI model. This layer is used to transfer data from the center of the network correctly. This layer is responsible to provide communication between two computers.
Transport layer is also called segment unit.
Its functions
The main function of the transport layer is to transmit data from one computer to another.
When it recieve the message from upper layers, it divides the message into very abstract segments. Each segment has a sequence number by which each segment can be easily identified.
Transport layer provides two types of service: -
connection oriented and connection less.
It performs both the functions of flow control and error control.
Session layer
Session layer is fifth layer of the OSI model, which controls connections between most computers.
The session layer provides a session for communication between two devices, that is,
In world wide web(www) when any user login to any web application or website the session is created between the user's computer system and websites server.
Simply the main function of the session layer is to see how the connections are established, maintained and terminated.
Its function
The session layer is acts like a dialog controller.
It fulfills the task of synchronization i.e whenever an error occurs in the transmission, the transmission is repeated again.
Presentation layer
Presentation layer is the sixth layer of the OSI model. This is used for encryption and decryption of data. It is also used for data compression.
Functions
The function of this layer is encryption. It is used for privacy.
To read full encryption, click on the link below.
what is encryption
Its main function is also compression. Compression is very important because we can reduce the size of the data by compressing it.
Application layer
Application layer is the seventh or highest layer in OSI model. The main function of the application layer is to provide an interface between our actual application and other layers.
This is closest to the end user. Various Protocols like SMTP HTTP FTP and NFS come under this layer.
Application layer controls how an application accesses the network.
functions
Through the application layer, the user can access the files from the remote computer and retrieve the files.
It provides the facility to forward and store email.
Through this, we can access the directory from the database.
There are 7 layers in the OSI model, it is a bit difficult to remember them, so below you have been given an easy way so that you can remember it easily: -
P-Pyare (Dear)
D-Dost (friend)
N-Naveen (Naveen)
T-tumhari (yours)
S-Shaadi (Wedding)
P-Pe
A-Aaunga (I will).
Advantage of OSI model
Its benefits are as follows: -
1: - This is a generic model and is considered a standard model.
2: - OSI model layers
That is, it is very specific for services, interfaces, and protocols.
3: - It is a very flexible model because any protocol can be implemented in it.
4: - It provides both connection oriented and connection less services.
5: - It implements divide and conquer technique in which all services work in different layers.This makes easy to maintain and administrate OSI model.
6: - All the layers are separated snd ekrks independently if one layer modified so it does not affect other layers.
7: - It is very secure and adaptable.
Disadvantage of OSI model
1; - It does not define any particular protocol.
2: - It is sometimes difficult to implement new protocols because this model was made before the invention of these protocols.
3: - In this there is duplication of services such that both transport and data link layer have error control method.
4: - All these layers are interdependent on each other.
Characteristics of OSI model
This model is divided in One upper layers and the other lower layers.
Upper layer handles application related issues which applies only to software.
The lower layers of OSI model handle issues related to data transport.
The main function of the physical layer is to place the data or information in the physical medium.
keep learning ………
Request: - Tell us how you liked this post of osi model and share it with your friends. If you have any question related to this or you have questions about any other subjects, then you can comment by commenting. I will publish it on the website for a couple of days.
No comments :
Post a Comment